The Maple Leafs held a moment of silence before their playoff game Monday in honour of those affected by the deadly incident involving a van and pedestrians in north Toronto earlier in the day.

The starting lineups of the Leafs and the Boston Bruins stood on their blue lines while the Air Canada Centre crowd stood in silence as a photo of Toronto's skyline flashed on the scoreboard.

The American and Canadian anthems were then sung, with singer Martina Ortiz-Luis dropping her microphone and letting the crowd take over the lyrics of O Canada during the second verse.

The Bruins expressed their condolences over Twitter before the game.

"Our thoughts are with all of those affected by today's tragedy. We stand with the City of Toronto during this difficult time," the team tweeted.

Roads were closed around the Air Canada Centre and there was more security inside the arena for Game 6 of the Eastern Conference quarterfinal in response to the incident that police say killed 10 people and injured 15 others.

Other Toronto teams — including MLB's Blue Jays, Major League Soccer's Toronto FC, the NBA's Raptors, the CFL's Argonauts, and the American Hockey League's Toronto Marlies — also tweeted messages of support, as did the NBA's Washington Wizards, who play the Raptors in Toronto on Wednesday in Game 5 of their first-round playoff series.

NHL commissioner Gary Bettman offered his condolences in a statement tweeted by the league.

Maple Leaf Sports and Entertainment issued a release announcing additional security measures at ACC hours after a van mounted a sidewalk and struck multiple people on a busy stretch of Yonge Street between Finch Avenue and Sheppard Avenue.

MLSE did not provide details on what the extra security inside the arena entailed.

Some 90 minutes before the opening faceoff, there was a heavy police presence around the rink and concrete slabs had been placed at a major intersection to block access to the sidewalk.

Fans attending games at the arena are already required to pass through a metal detector before games, and bags allowed into ACC can be no larger than 14-by-14-by-6 inches, smaller than an average backpack.

In addition to those watching the game inside the arena, a sizable crowd was expected to assemble outside in Maple Leaf Square.

The release did not say if the same measures will be in place for Wednesday's NBA playoff game between the Raptors and the Wizards.

Toronto police tweeted that "similar road closures" around the arena could be expected for Wednesday's game.